Concise Enantioselective Synthesis of Furan Lignans (-)-Dihydrosesamin and (-)-Acuminatin and Furofuran Lignans (-)-Sesamin and (-)-Methyl Piperitol by Radical Cyclization of Epoxides
作者:Subhas Chandra Roy、Biplab Banerjee
DOI:10.1055/s-2005-872173
日期:——
Enantioselective syntheses of furan lignans (-)-dihydrosesamin and (-)-acuminatin and furofuran lignans (-)-sesamin and (-)-methyl piperitol were achieved in up to only three steps in 43%, 42%, 63%, and 60% overall yield,respectively, with high optical purity through stereoselective intramolecular radical cyclization of suitably substituted epoxy olefinic ethers using bis(cyclopentadienyl)titanium(III)
呋喃木脂素 (-)-二氢芝麻素和 (-)-acuminatin 以及呋喃木脂素 (-)-芝麻素和 (-)-甲基胡椒醇的对映选择性合成只需 43%、42%、63% 和通过使用双(环戊二烯基)氯化钛(III)作为自由基引发剂对适当取代的环氧烯烃醚进行立体选择性分子内自由基环化,总产率分别为 60%,具有高光学纯度。关键中间体手性环氧醇 4 采用 Sharpless 动力学拆分法制备。钛 (III) 引发剂由市售的二氯化二茂钛和四氢呋喃中的活化锌粉原位制备。